Sunday, November 30, 2008

Polyunsaturated Fat Intake: Effects on the Heart and Brain

I'm revisiting the topic of the omega-6/omega-3 balance and total polyunsaturated fat (PUFA) intake because of some interesting studies I've gotten a hold of lately (thanks Robert). Two of the studies are in pigs, which I feel are a decent model organism for studying the effect of diet on health as it relates to humans. Pigs are omnivorous (although more slanted toward plant foods), have a similar digestive system to humans (although sturdier), are of similar size and fat composition to humans, and have been eating grains for about the same amount of time as humans.

In the last post on the omega-6/omega-3 balance, I came to the conclusion that a roughly balanced but relatively low intake of omega-6 and omega-3 fats is consistent with the diets of healthy non-industrial cultures. There were a few cultures that had a fairly high long-chain omega-3 intake from seafood (10% of calories), but none ate much omega-6.

first study explores the effect of omega-6 and omega-3 fats on heart function. Dr. Sheila Innis and her group fed young male pigs three different diets:
  1. An unbalanced, low PUFA diet. Pig chow with 1.2% linoleic acid (LA; the main omega-6 plant fat) and 0.06% alpha linolenic acid (ALA; the main omega-3 plant fat).
  2. A balanced, low PUFA diet. Pig chow with 1.4% LA and 1.2% ALA.
  3. An unbalanced, but better-than-average, "modern diet". Pig chow with 11.6% LA and 1.2% ALA.
After 30 days, they took a look at the pigs' hearts. Pigs from the first and third (unbalanced) groups contained more "pro-inflammatory" fats (arachidonic acid; AA) and less "anti-inflammatory" fats (EPA and DHA) than the second group. The first and third groups also experienced an excessive activation of "pro-inflammatory" proteins, such as COX-2, the enzyme inhibited by aspirin, ibuprofen and other NSAIDs.

The most striking finding of all was the difference in lipid peroxidation between groups. Lipid peroxidation is a measure of oxidative damage to cellular fats. In the balanced diet hearts, peroxidation was half the level found in the first group, and one-third the level found in the third group!
This shows that omega-3 fats exert a powerful anti-oxidant effect that can be more than counteracted by excessive omega-6. Nitrosative stress, another type of damage, tracked with n-6 intake regardless of n-3, with the third group almost tripling the first two. I think this result is highly relevant to the long-term development of cardiac problems, and perhaps cardiovascular disease in general.

another study with the same lead author Sanjoy Ghosh, rats fed a diet enriched in omega-6 from sunflower oil showed an increase in nitrosative damage, damage to mitochondrial DNA, and a decrease in maximum cardiac work capacity (i.e., their hearts were weaker). This is consistent with the previous study and shows that the mammalian heart does not like too much omega-6! The amount of sunflower oil these rats were eating (20% food by weight) is not far off from the amount of industrial oil the average American eats.

A third paper by Dr. Sheila Innis' group studied the effect of the omega-6 : omega-3 balance on the brain fat composition of pigs, and the development of neurons
in vitro (in a culture dish). There were four diets, the first three similar to those in the first study:
  1. Deficient. 1.2% LA and 0.05% ALA.
  2. Contemporary. 10.7% LA and 1.1% ALA.
  3. Evolutionary. 1.2% LA and 1.1% ALA.
  4. Supplemented. The contemporary diet plus 0.3% AA and 0.3% DHA.
The first thing they looked at was the ability of the animals to convert ALA to DHA and concentrate it in the brain. DHA is critical for brain and eye development and maintenance. The evolutionary diet was most effective at putting DHA in the brain, with the supplemented diet a close second and the other three lagging behind. The evolutionary diet was the only one capable of elevating EPA, another important fatty acid derived from ALA. If typical fish oil rather than isolated DHA and AA had been given as the supplement, that may not have been the case. Overall, the fatty acid composition of the brain was quite different in the evolutionary group than the other three groups, which will certainly translate into a variety of effects on brain function.

The researchers then cultured neurons and showed that they require DHA to develop properly in culture, and that long-chain omega-6 fats are a poor substitute. Overall, the paper shows that the modern diet causes a major fatty acid imbalance in the brain, which is expected to lead to developmental problems and probably others as well. This can be partially corrected by supplementing with fish oil.

Together, these studies are a small glimpse of the countless effects we are having on every organ system, by eating fats that are unfamiliar to our pre-industrial bodies. In the next post, I'll put this information into the context of the modern human diet.


Jeff said...

Hey Stephan,

Great post, as usual. I am really curious how I can translate this into the diet for my 2 children. Depression and other mental issues run in our families, which I think simply means we have a genetic propensity for it in the environment of the standard American diet. I would like to have those issues be eliminated by healthy eating.

I have them on a evolutionary model, for the most part. They eat little sugar, wheat and veg oils when we have them at home, but when they are in school I have little control and it is mostly crap that they think is good since it follows the USDA. The other issue I have is the meats we eat are argicultural. We have started getting grass fed beef, but other meats and poultry are harder for us to come by. The best we do is Bison and wild fish. I think that in this arrangement it is important that I supplement with both of them. If you or any of your other reader have any suggestions I would love to hear it.

Thanks as always for your great information here.


Stephan Guyenet said...

Hi Jeff,

I think it's great that you put so much thought and effort into your family's diet. Your diet is WAY ahead of the curve.

The best way to keep fats balanced is to avoid omega-6 rich vegetable oils, in my opinion. If you think they're getting too much of that at school, you could consider supplementing them with a little high-vitamin cod liver oil. Wild fish is also great, actually it's probably the best source of omega-3 because it comes with so many other nutrients!

Grass-fed butter is also a good addition to a healthy diet because it's an easier way to get K2 than where HGs got theirs: a variety of organs, bugs, etc. I know it's not paleo, and some people do really have trouble with dairy, but it's almost always the protein or lactose portion they can't handle. So if that's a concern, butter is almost pure fat, and ghee is literally pure fat.

Jeff said...

Glad to hear about the butter. I just found a pastured cow organic butter. I will be switching over completely for my whole family.

Thanks again.

Robert Andrew Brown said...

Great Post Stephan, and thank you very much for the mention. You write very well and put things simply and clearly. Your posts are always thought provoking.

I am re-writng at the moment to include general improvements, intake recommendations, and a more detailed examination of the oxidative stress issues and mechanisms.

(I apologise for my poor punctuation - I had an asymptomatic tooth abscess that had been there a while (maybe 2 years) whilst writing. Maybe it added to a tendency for word blindness.(-:)

At the time of writing I did not put figures on how much Omega 6 was ideal as intake as 1/2 - 2% of calories seemed so much at odds with the popular message.

Having found more papers, and populations with a low Omega 6 intake I think it is reasonable to state that Omega 6 plant based intake should be between 1/2% and 2% of calories.

I have to pay tribute Professor Bill Lands who has been bravely explaining about the impact of excess Omega 6 for maybe 30 years and is one of the true pioneers in the field.

This is Bill Lands, and he inspired this NIH lecture series and the recording of it.

You will find more NIH videos on the impact of Omega 3s and 6s on various aspects of health on my resource page.


There is a suggestion that some population groups like Inuit and Celts may exhibit poorer conversion.

There is also a breast cancer trial which suggests genetic variants in Omega 6 fat elongation and metabolism impact on disease risk, which may have a wider application given the common pathways.

There are also a long list of factors that block conversion of the plant fats to the longer chain fats.

Moderate alcohol consumption in the absence of a supply of Omega 3s is extremely damaging.

Fat an analyses of those with a range on mental and behavioural issues including depression, self harm, suicide, bipolar, and others, often have low long chain Omega 3s and high 6s.

Minerals are essential to fat metabolism. Mineral intake is falling due to soil depletion. In the shoreline diet intake of minerals and iodine from shellfish would have been higher than current dietary intakes. Minerals impact on mental function.

Omega 6s plant based fats are everywhere in processed food including `healthy` food like grain bars, so avid label reading is a must.

Balancing applies to the plant based fats.

The body will safely deal with any excess of long chain Omega 3.

Robert Brown


Omega Six The Devils Fat

Anna said...


I share your concern about the UDSA recommended foods served at school. Our school doesn't even have a kitchen; the heat & serve foods are centrally made and distributed to the elementary schools. Most are garbage - chicken nuggets, mac & cheese, bean, rice & cheese burritos, HB & CB made with soy TVP, etc. They have "improved" the program with a salad bar and some "fresh" produce, but they continue with packaged syrupy fruit cups, low fat plain and chocolate milk and juice, graham crackers & animal crackers, etc. And there is a daily delivery of pizza, I think from Domino's, which is a pretty poor excuse for pizza, as well. You can imagine that there are kids who eat pizza or chicken nuggets and juice or chocolate milk every day and nary a veggie.

I would consider pushing for a program more like the ones that Alice Waters and Jamie Oliver have publicized, but I generally find that I would be viewed as Chicken Little. Our local parents are apparently happy with the program. And some of what I've seen in the lunches packed at home would make you cringe, too - all or mostly individually wrapped items from warehouse stores, like manufactured PB& J sandwiches on white dough bread (who can't make a PB & J for cryin' out loud?), Lunchables, etc. Is it any wonder nearly half of my son's class is overweight or constantly sick with something?

So, my son doesn't eat from the school lunch program, though there are some rare exceptions a couple times a year (maybe 4?) when I just didn't get my act together :-). I prepare his lunches at home in just a few minutes (rarely more than 5 minutes) each morning while he eats his breakfast, but I try to have easy options available for him to eat in the fridge all the time, which makes packing the lunch easy and fast.

We use a Japanese-inspired "bento" style lunch box system (Laptop Lunch) that is great for keeping foods fresh, appetizing, and separated (frozen gel pack, too). He drinks water from s/s bottle while at school.

Lunch items vary but might include some diced chicken meat, slices of leftover roast bison or beef, shredded BBQ pork shoulder, hard cooked eggs or egg salad (homemade mayo with olive oil), cut veggie sticks or celery with cream cheese or homemade cheese spread, cubes of a nice aged cheddar or other cheese, sometimes salami slices or liverwurst, fruit (orange slices, apple slices dusted with cinnamon, whole tangerines, soaked & dried nuts, leftover frittata, etc. About twice a week he has a sandwich made with sprouted flourless multigrain bread (no soy or added gluten). That is our compromise; I'd like to eliminate the bread but I'm ok for now with this. I used to send home-flavored whole milk yogurt in screw top plastic containers, but he doesn't eat it much now at school so we save that for an after-school snack or after dinner. I don't send anything that needs to be hot or warm; it's either room temp or slightly chilled from the frozen gel-pack. Generally he likes things that are easy and quick to eat without a mess and don't require a lot of fuss with containers; he wants to get out on the ball fields with his friends (somedays they play first, then eat). He eats more after school most days than at lunchtime.

So if you aren't packing your kids' lunches, you might consider doing it at least a few days a week. But it takes a while to think outside the sandwich box, so go slow, and plan a prep and packing strategy long before the morning time crunch (make extras when you make dinner and make sure the containers are available when you need them). Let us know how it goes.

Anna said...


Fred Hahn just published a book on strength training and healthy eating for kids that fits very well with the diet views of Stephan and most of the readers of this blog, Strong Kids Healthy Kids. Hahn previously co-wrote Slow Burn with the Drs. Eades of Protein Power. Dr. Mary Dan Eades has a review of the new kids book up on her blog at www dot proteinpower dot com. There are recipes in the book, too.

I forgot to mention one of my son's favorite lunch items - a chilled small or half artichoke with mustard mayo (homemade with olive oil) for dipping. Pulling leaves is fun for kids, so I always make a couple extra when I am steaming. And while artichokes aren't cheap in many distant markets, they are a great veggie treat now and then. At least fresh artichokes remain seasonal.

Unknown said...

Robert, can you comment on the body's handling of "excess Omega 3"? I have actually been curious about that, as Weston Price mentioned that overdosing on fish oil was possible.


Debs said...

That piece from the first study about the unbalanced diets excessively activating COX-2 is interesting. Weren't we wondering recently if there might be an n-6/migraine connection?

Food Is Love/Seattle Local Food

Stephan Guyenet said...


Yes, anything that's helped by COX-2 inhibitors like aspirin is potentially caused by excessive n-6 to begin with.

Aaron Blaisdell said...


Thanks for the great lunch ideas for the kids! I have a 3 year old and a 3 month old. I try to feed my 3 year old a healthy diet, but she is so addicted to carbs, especially gold fish crackers, bread, mac n cheese, etc. I'm slowly but surely making progress by getting her to accept more meat, but for some reason she really resists it. Even chicken! I sneak high-vitamin cod liver oil and butter oil (both from Green Pastures) into her lunch every day to make sure she's got a good supply of the right vitamins.

It's a very challenging time to be a parent as far as nutrition is concerned.

Stephan Guyenet said...


Up to 2% LA sounds reasonable to me, and is consistent with the WAPF recommendations of keeping total PUFA under 4%. I've found it's actually pretty difficult to achieve in the modern world. I've been keeping track and I've gotten my LA down to 2% recently, n-3 around 1%.

That's by making butter, beef tallow and coconut my main fats, replacing almonds with hazelnuts, and sometimes eating duck eggs rather than chicken eggs. But I also eat a lot of fat (50-60% of calories), so it would be easier for someone who eats less than me.

E said...

Excellent article. Excellent blog. Thank you!

Scott said...

huh. duck eggs instead of chicken eggs, eh? i'm curious now.

David said...

How do we know these effects are specific to polyunsaturates rather than to any high fat diet?

Robert Andrew Brown said...


ISSFAL suggest 2% with an upper limit of 3%.

But as well as all the reasoning some eminent Professors in the field are saying 2% as against 3% as a maximum.


Essentially because of the biology and function of Omega 3 and 6.

All fats have different functions and uses in the body.

By changing the mix you change body function.

Populations on high fat on non-westernised diets seem to do very well and are free of western conditions. So the issue is not simply high fat.

The question is what has changed in our modern high fat diets, that could account for the increases in western conditions. The answer is excess Omega 6 and a lack of Omega 3.

Omega 3 and 6 act in a dance of opposites. They are the raw material of huge families of very influential chemicals that control inflammation, destruction and repair of tissue, link into immune function, control sex hormones and a myriad of other functions.

Other fats are equally essential and have many functions but are not in the same ball park in terms of functional influence and do NOT control inflammation, destruction and repair of tissue, link into immune function, control sex hormones and a myriad of other functions.

All fats except the Omega 3 and 6 fats can be made from scratch from the body. So Omega 3 and 6 are external dietary controllers of body function through diet.

We have massively increase Omega 6 intake beyond anything seen in our history and similarly reduced Omega 3s.

To that you can add depletion of minerals including iodine, and some essential vitamins like A D an K as Stephan so rightly a regularly points out.

Robert Brown

Author Omega Six The Devils Fat

Jeff said...


Thanks for your long and detailed comment. It helped a lot. I am going to start packing lunches. The only thing I am worried about there is that sometimes schools won't let you due to peanut allergies.

I will check out Fred's book. I saw his other book in the book store, but the exercise stuff I haven't bought into yet. I do more explosive exercises instead of the slow stuff. I am open to anyone's thoughts on the matter, however and am very interested in what he recommends for the little ones.


Stephan Guyenet said...


In addition to what Robert said, take a look at the first diet group in the first pig study. It was the lowest in fat of the three, but it had twice as much lipid peroxidation and significantly more inflammatory signaling than the higher-fat diet balanced in omega-3 and 6.

By the way, high-fat diets don't seem to agree with rodents very well, but the same is not true of humans. We have a long history of high-fat diets, and the recent avalanche of successful low-carb studies emphasize that. I think it's also worth pointing out that rodents do much better on a high-fat diet where the fat is highly saturated than one where the fat is n-6 rich vegetable oil.

Stephan Guyenet said...


Duck eggs are lower in PUFA and higher in just about everything else.

Anonymous said...

Stephan, yours is truly an excellent blog, which I regret not having discovered before today.

If I may, I would like to bring up Ray Peat's writings on n-3s. His article-filled site is easily found by looking up his name. As one of the earlier advocates for the health benefits of saturated fats and perhaps one of the first preaching in favor of coconut oil in particular, Peat shares many of the views posited by Mary Enig at the Weston Price Institute, but they have had sometimes contentious debate over n-3s.

Peat points to research supporting his belief that all PUFAs are toxic, and in his articles he argues and cites much research about the long-term physiological effects of n-3s beyond their initial anti-inflammatory effects in the short term.

He does not convince Dr Enig, but his dissenting arguments and citations on the subject are at least thought-provoking.

Stephan Guyenet said...

Thanks Cytotalker. I am familiar with Ray Peat. A lot of what he says makes sense. I have a hard time believing some of it though. For example, the idea that the amount of PUFA we would have eaten as hunter-gatherers is immunosuppressive. It's just hard to swallow the idea that we aren't adapted to the diet we've been eating for a million plus years.

I think Peat and the WAPF are in agreement that low total PUFA is best. If I understand correctly, Peat would say to avoid nearly all PUFA including n-3, while the WAPF would say to balance n-6 and n-3 and keep the total low. I think there's enough evidence of the benefits of n-3 that the WAPF stance makes the most sense to me. I'll go even further: I think it's OK to eat more n-3 in the context of a carnivorous diet like the Inuit had. But n-6 should be kept low no matter what.

Peat also has a point that some of the effects of fish oil may be short-term. But I think there is also enough evidence of long-term benefit to justify small doses of omega-3.

Robert Andrew Brown said...

Re avoiding long chain Omega 3.

Like Stephan I think Professor Peat has some great ideas on saturated, and oxidation but think it is important to separate omega 3s from 6s.

Dolphins do well on a VERY high long chain Omega 3 diet.

Kitavans in the trial found be Stephan do well on a high fish intake.

I agree that potentially long chain DHA is highly susceptible to oxidation but 25% of the brain fat is [or should be] DHA, which suggests the body has a number of sophisticated protection mechanisms against unwanted oxidation of DHA. If DHA was not protected brains would not work – they would be oxidative chaos.

This is one trial quoted by Professor Ray Peat and they used 25% of fat as fish oil which is very high and likely beyond the body’s protective capabilities.

Effect of type of dietary fat and ethanol on antioxidant enzyme mRNA induction in rat liver

Fish oil comes from fish and shell fish which are high in minerals iodine A and D etc which are part of the protective framework I suspect. Shore dwellers would have had high levels of long Omega 3s, mid chain saturates, and low 6, and I feel that providing we get the antioxidant precursors in fish sensible long chain Omega 3 intake is more beneficial than damaging. That general observation is supported by a wealth of trials on various western conditions.

Again many thanks to Stephan for all the time and hard work he puts into this blog.

Robert Brown


Omega Six The Devisl Fat

Bryan - oz4caster said...

Stephan, I just recently took a look at PUFA in animal meats as a percentage of total calories. It's interesting that ruminants, even heavily grain fed, still have low PUFA, whereas omnivores like pigs and chickens seem to greatly increase the PUFA content in the meat when fed a lot of grain, as is common practice. Typical commercial pork runs around 6% to 7% of calories as PUFA, while wild boar is only 3.6%. That's roughly double. Typical commercial chicken and turkey runs around 6% to 12% PUFA calories. I haven't found a comparable wild figure. For salmon, wild was 8.2% and farmed was 19.3% - more than double. I posted the full list in Fat Follies.

Maybe humans tend to accumulate more dietary PUFA, like other omnivores.


Stephan Guyenet said...


Thanks for pointing that out. Humans will accumulate n-6 in large quantities, but not n-3. I suppose that's true of certain other animals as well, but not ruminants.

Robert Andrew Brown said...
This comment has been removed by the author.
Robert Andrew Brown said...


Thanks for the list it is really useful.

I look forward to looking at your site.

Cattle certainly develop an Omega 3 6 imbalance if fed on grain compared to pasture.

Pasture fed sheep have Omega 3 ALA and Omega 6 LA within the 1:2 ratio, but grain fed cattle have much higher 6 than 3,and that shows in dairy products too (based on an examination of Swiss mountain cattle and cheese.)

I have not come across figures that would allow comparison between grass fed and grain fed cattle as to absolute quantity of Omega 6 stored.

Storage of EFA in wild animals is very seasonal which would be reflected to a certain extent in grass fed live stock.

Omega 6 in wild boars, rabbits etc would follow food chain availability. I have seen a suggestion that wild rabbits can accumulate high levels of Omega 6, presumably when plants are Omega 6 rich. More reading required (-:.


Thanks for the link. Your site looks great and full of useful tips. More reading to look forward to(-:.

kortina said...

Hi Stephan,

This is off topic and not relevant to this post, but I couldn't find a contact form so comment was the only way to pose this question.

I came across an interesting food called quinoa at the salad bar today

For some reason, as I'm eating this, I was thinking "I wonder what the whole health source guy thinks of quinoa"

Would love to hear your thoughts on quinoa's nutritional value and how it relates to diseases of civilization you are always speaking of.

Also, love the blog and have been following for months. Keep it up.


Unknown said...


One (or two?) of the civilizations studied by Weston Price which exhibited excellent dental health and none of the diseases of civilization made heavy use of quinoa. I'm not sure what it provides, so I don't know what else you need to eat to get complete nutrition, but it does not appear to be harmful to humans the way sugar, wheat and vegetable oils are.

Best regards,

kortina said...

Thanks for the reply, Brock.

Debs said...


Which civilizations? I'm pretty sure the only grains eaten by the populations he studied were oats (in Scotland) and sourdough rye bread (Swiss Alps). Personally, I eat a decent amount of quinoa but I always soak and rinse it, like I do with any grain.

Food Is Love/Seattle Local Food

Stephan Guyenet said...


Brock hit the important point, but I'll add a little more. Quinoa is not technically a grain, it comes from a broad-leafed plant in the goosefoot family (Chenopodium). It's very nutritious. It has more protein than any grain, and the protein is complete (not lacking any essential amino acids). The one problem is it's rich in omega-6 linoleic acid. It should be soaked before cooking like a grain or legume.

Unknown said...

The South American ones. I think it was just the Amazonian tribe, but the Peruvians may have eat it too - I can't remember now.

Anna said...

I use a bit of quinoa now and then. It has a much better amino acid content than other grains and is a bit lower in starch. And it's gluten-free. But it still is pretty starchy, so I don't go crazy because I have to watch my blood glucose level.

I've seen quinoa pasta, but it never is 100% quinoa so I don't buy it. I've seen quinoa flour, which I've used a little bit, and also rolled quinoa flakes, similar to rolled oats. That's also good for thickening (but still, I use it in small quanities because of the starch content).

I use quinoa a couple of ways. I always rinse it; it can have saponins remaining on the outer layer, which can taste slightly bitter (I read somewhere that in the US quinoa is generally already rinsed, though). I soak and sprout quinoa, then toss a 1/4 cup or so in a green salad.

I've added it to my son's soaked, cooked oatmeal for breakfast to boost the protein content a bit.

I also make quinoa instead of wheat for tabouli, though I go pretty heavy on the parsley and diced tomatoes ratio compared to the quinoa.

I use quinoa instead of cous-cous, but again, not in huge quanities.

When I make stews and soups with rich meaty sauces and broths that beg for a thickener or something to soak up excess liquid, then I might toss in a handful or two of quinoa at the end of simmering. It takes about 10 minutes to cook through. The little round bits add a nice texture, too.

Stephan Guyenet said...


I've discovered using quinoa for tabouleh and soups too. If you cook it for a long time in a soup, it softens and puffs up like rice and thickens it nicely.

Anna said...

We had Roman Stew with bison shanks and round steaks tonight (eastern spices), simmered in the Crockpot 10 am -6 pm (rich marrow bones). I cooked a half cup of quinoa in 1 cup of chicken broth, seasoned with seas salt, kelp granules, and flaked sea vegetable (looks like chopped parsley). Even spooning a bit of the quinoa into the stew to soak up the broth, we had quinoa left over.